This invention relates to an interventional catheter comprising a catheter tube having two superposed layers of materials secured in relation to one another and with mechanical properties differing from one another, a longitudinal lumen in said catheter tube for the sliding fit of a guide wire, and a balloon with a proximal end and a distal end, whereby the distal end sealingly surrounds said catheter tube, whereby the catheter tube has an inner layer forming the longitudinal lumen and an outer layer forming the outer surface of the catheter tube.
Over the wire catheters are now widely used for interventions such as percutaneous transluminal angioplasty. A problem with these catheters is that the guide wire may clog into the longitudinal lumen of the catheter; as a result, the guide wire may follow the balloon upon withdrawal thereof after the inflation procedure, thereby making it necessary to re-insert the guide wire into the threaded area of the blood vessel for re-positioning a balloon therein in case a second inflation is needed. Apart of this, the catheter has to achieve an acceptable compromise between the requirements of some stiffness to assure good pushability and of some flexibility to assure kink resistance. In addition, the catheter has to permit safe attachment of the balloon to the catheter tube.
The document WO 92/11893 describes an intra-aortic balloon apparatus comprising a hollow catheter in which is located an elongated member forming a central lumen extending out of the catheter at the distal end thereof. An aortic pumping balloon is positioned over the elongated member; the distal end of the balloon is bonded to a tip affixed to the distal end of the elongated member, and its proximal end is bonded to the distal end of the catheter. In order to achieve a balance of flexibility and remains and to avoid kinking, the elongated member is formed of an inner layer comprised of a soft elastomeric material to impart flexibility to the tubing, and the outer layer is comprised of a hard plastic material to impart structural support to the elongated member. The combination of these two layers is made to achieve a very durable and flexible structure exhibiting a low kink radius. This balloon apparatus cannot be loaded with a guidewire and moved into tortuous vessels with the guidewire loaded inside the elongated tube. The friction between guidewire and the elongated member increases distinctively when the elongated member is shaped into curves. The above procedure would therefore risk that the spiral wound guidewire could be captured in the soft elastomeric plastic material of the inner layer of the elongated member. Although the outer layer of the elongated member that is coextruded onto the inner layer is formed from nylon, a material which is directly weldable to a wide variety of materials, this balloon apparatus cannot be introduced into narrow vessels or arrow stenoses nor can it be passed through narrow punctures to enter the blood vessels. This is because of the relatively large profile of the folded balloon. The large P.rofile is due to the distal fixture of the balloon to the elongated member. The balloon is bonded to an intermediate tip element which in turn is bonded to the elongated member.
U.S. Pat. No. 4,323,071 describes a combination guiding catheter assembly and dilating catheter assembly. The guiding catheter assembly comprises a first flexible tubular member formed of a material with low coefficient of friction and high flexibility; as this first tubular member is too flexible to serve as a guiding catheter because it could not be properly manipulated in the body of a patient, a second tubular member made of a heat shrinkable tubing is provided to encase the first tubular member. The distal end of this assembly is preshaped to form a shape corresponding to the standard coronary catheter and the proximal end of the assembly is provided with attachment means to provide a leak-proof adhesive-free connection. The dilating catheter assembly is disposed within the guiding catheter assembly and comprises a first tubular member coaxially disposed within a second tubular member having formed thereon a balloon at its distal end, both these tubular members being made of shrink tubing; an annular flow passage between the first and second tubular members allows introduction of fluid into the balloon for inflation thereof. The proximal end of this assembly is inserted in an adapter body for connection to an appropriate syringe system. A dilator consisting of a flexible plastic tube with a teflon coated guide wire therein is used to position the guiding catheter assembly in the proper location. Within this frame, the guide wire is first inserted conventionnally into the blood vessel; the dilator is then positioned in the guiding catheter assembly to straighten it, and the dilator and guiding catheter are passed over the guide wire into the blood vessel; when the guiding catheter is in the proper location, the dilator and guide wire are withdrawn from the guiding catheter and the dilating catheter assembly can be inserted into the guiding catheter assembly, which operation is facilitated be the low coefficient of friction of the first tubular member of the guiding catheter assembly. A small guide wire may be utilized if necessary to precisely position the balloon of the dilating catheter assembly; if so, this small guide wire has to be inserted into the first tubular member of the dilating catheter assembly so that it extends from the distal portion thereof. This guide wire may be removed once the balloon is in the proper location.
This publication shows a catheter shaft made from a composited material that is achieved by heat shrinking. The material for the inner layer of the composite material is selected from materials rendering low friction. Any instrument inserted into a catheter shaft made from this composite material can easily be moved inside the shaft even after the shaft has been bent and is kept in narrow curves. The shaft for the dilation balloon catheter shown in this publication does not use composite material for its construction. It uses conventional material in one single layer. Because the balloon must be welded or otherwise securely bonded to the catheter shaft to withstand the extraordinary high inflation pressures used in angioplasty, the shaft material for this dilatation balloon catheter has to be selected for good bond characteristics and cannot be selected for good friction characteristics. Therefore this catheter still presents the problem that in tortuous vessels, when the catheter shaft has to follow numerous bends of the vessel, the guidewire can be captured in the shaft. This is specifically troublesome since the dilation catheter has to advance much deeper into the branched vessel system than the guiding catheter which in this publication is shown as made from composite material. For a dilatation catheter the length of the friction creating shaft is longer than the shaft of the guiding catheter and additionally the dilatation catheter shaft is exposed to more vessel curves.